Electronic device and circuit arrangement therefor



July 5, 1949. A. M. sKELLETT ELECTRONIC DEVICE AND 'CIRCUIT ABRANGEMENTTHEREFOR 2 sneetsh-sheet 1 Filed April 28, 1945 Fig. 3

INVENTOR.

T l E u. E y M W E E L IJuly 5, 1949. A. M. sKELLE'rT ELECTRONICDEVICEAAND CIRCUIT ARRANGEMENT THEREFOR Filed'April 2B, 1945 2Sheets-Sheet 2 MASTER OSCILLATOR RADIAL BEAM TUBE INVENTOR. ALBERT M.SKE'LLETT Patented July 5, 1949 ELECTRONIC DEVICEAND CIRCUIT ARRAN GEMENT THEREEQB Albert M. Skellett, Madison, N. il., ass'ignorv to NationalUnion Radio N. J., a corporation of D Corporation, Newark, elawareApplication April 28, 1945, .Serial No. 590,912,

(Cl. SI- 91) 4 Claims.

The present invention relates to a method lof generating the tones foran electronic organ, more particularly to a tone generator systememploying Va plurality of radial beam vacuum tubes-as the tone source.In my prior Patent No. 2,217,774, granted October 15, 1940, there isdescribed an electronic switching tube wherein an electron beam isdeflected to impinge in succession upon a plurality of targets oranodes. Means are provided for shifting or rotating a magnetic eldbetween the cathode and the targets, the lines of force of the fieldbeing normalto the longitudinal axis of the cathode. A tube of thischaracter may be employed in a variety of signal translating systems,as, for example, a multiplex telephone system.

In my Patent No. 2,320,756, issued June 1, 1943, I disclose theapplication of a type of radial beam tube as a frequency multipliercapable of producing an alternating current having a frequency withinthe limits of the Vordinary musical scale which may be used as a staticgenerator employed as a source of stone for various purposes.

A general description as to structure and characteristics of mymagnetically focused radial beam vacuum tube involving the foregoingconstruction is described in the Journal of Applied Physics, vol. 15,No. 1'0, pp. 704-709, October 1944.

An object of the present invention is the adaptation of my prior radialbeam vacuum tube construction and circuit arrangements, as set forth in`the foregoing references, to the problem of generating tones forelectronic organs, such as described in the Hammond Patent No.1,956,350, granted April 24, 1934.

The instrument disclosed in the aforesaid Hammond Patent No. 1,956,350operates upon the principle of synthetically producing electrical wavesof the desired frequency, and including various proportions of harmonicsnecessary to produce a tone of the desired quality or tone color. Themeans for generating the electric currents of diiferent frequenciescomprise a plurality of alternators, one for each frequency necessary toproduce the fundamental of the tempered musical scale. The rotors of thealternators are driven from a constant speed motor.

In the embodiment of the Hammond organ described in the aforesaid patentthere are eighty-nine alternators, there being seven different shapes ofrotors employed, the rotors hav ing respectively 2, 4, 8, 1'6, .32, 64and 128 high points Whichrepresent the harmonic tones of thefundamental." A selector'mechanism is provided for selectingthe severalfrequencies constituting a fundamental land its harmonics.

From the foregoing lit will be seen that in the Hammond 'organalternators produce electrically the vtones Ibythe mechanicalcontroland/or operation of the vmechanisms constituting the system. Thesemecha-nical parts have substantial inertia which, in turn, indirectlyproduce a source of distortion from the theoretrical frequency of notesin the musicalscale with a consequent distortion `of tone qualityl It istherefore an object of the present invention to substitute a modiiiedIform of my prior radial Abeam vacuum tube as the tone generator inplace `of the alternators employed by Hammond. More generally I proposethe application of a radial beam vacuum tube for the generation of tonesfor electronic organs.

Another object of -the invention is the provision of tone generatingmeans 'free of inertia and without mechanical ymoving parts, said meanspreferably `taking the lform of one or more specially designed radialbeam vacuum tubes electricallyassociated with a master oscillator whichmay be individual .to a given fundamental and its harmonics.

A special feature .of 'the invention is the provision of a radial beamvacuum tube having a screen element provided with one or more bands,each comprised of `a series lof apertures coaxially arranged with.respect to the cathode. The apertures of each Aseries are ldesigned toproduce sinewave currents when the electron beam, which is substantiallyrectangular in cross section, sweeps across them. By varying the numberof apertures in the several 'ba-nds., the frequency of the sine wavesmay-.be altered to produce the musical notes and their harmonics..

'Other objects of :the invention will manifest themselves as thedescription proceeds.

Referring to the accompanying drawings:

Fig. 1 is a perspective View of the screen element of a radial bea-mvacuum tube embodying a feature of the .present invention;

Fig. 2 isa perspective view -of an electron discharge Ideviceillustrating one embodiment of the invention, :a portion of theenclosing envelope being broken away fand, also portions of theelectrode assembly, to, lshow the internal structure more clearly;

Figure 3 is a diagrammatic view showing the screen element., asillustrated in Fig. 1, unrolled;

4is a top view, partly insection, of a magnetic :field producingstructure utilizing two phase current;

Fig. is a diagrammatic View of the circuit arrangement for operating apair of my electron beam tubes in connection with a master oscillator;and

Fig. 6 is a side view of the magnetic system shown more particularly inFig. 4.

Referring to the drawings, more particularly Figs. 1 to 3, it will benoted that I have illustrated the invention embodied in a simplifiedform of my prior radial beam vacuum tube, and only so much of thecircuit organization is diagrammatically and/or schematicallyrepresented in Figs. 4 and 5 for one to comprehend the features and/oroperation of my tone generating system as applied to a common form of anelectronic organ.

The tube comprises an envelope i, having mounted therein an electrodeassembly, which may be referred to generally by the reference character2. The electrode elements are supported between a pair of spacedinsulating members such as mica discs 3, and comprise respectively acylindrical indirectly heated cathode d, surrounded by a coaxialcylindrical screen element E. Encompassing the screen 5, are a pluralityof spaced, ring-like targets or anodes 6, l', 8 and 9. The electrodeassembly 2 may be conventionally supported from a stem l l terminatingin a press l2. Extending through the press I2 are conductors i3 forelectrically connecting the electrodes forming the assembly 2 in theoperating circuits comprising the circuit organization of the tonegenerator system.

The screen element 5 is provided with series of apertures, each seriesconstituting an individual pattern and forming bands l5, I6, I7 and I8coariially arranged with respect to the cathode and oppositely disposedwith respect to a given one of the anodes 6 to e. When the screen e isunrolled the several series of apertures have a sine-wave shape varyingin the number of the peaks as determined by the frequency of the note orharmonic desired. Stating somewhat differently what has just beendescribed, there are two apertures it in the series constituting theband l5, which is opposite the fundamental frequency anode 6, and whenthe screen element 5 is unrolled the form of the apertures is a sinewave and they extend the full length of the screen. 1n a similar mannerthe apertures i4 comprising the band le represent the second harmonic ofthe fundamental, and there are four apertures in the series whichproduce a sine-wave form of the same amplitude and of twice thefrequency as that of band I5. The apertures comprising bands il and I8are likewise multiplied by two, resulting in eight and sixteen peaksrespectively, which are also of the sine-wave form, and represent thefourth and eighth harmonic of the fundamental tone. The production ofthe harmonics of the several fundamentals comprising the musical scalewill hereinafter be more fully explained, but it is significant to noteat this point the relation between the shape of the apertures lll andthe wave form. The present adaptation of my tube contemplates thefocusing of the electrons in a double beam in of a substantialrectangular cross section so that as the beam sweeps across theapertures, the amplitude of the current to the anode has the form of asine-wave modulation of a selected frequency.

The focusing of the electron beam lil is 0btained by the magnetic field.The type of electrostatic eld I prefer to employ in the presentapplication has cylindrical symmetry and is secured by putting apositive potential on the screen and also on all of the anode elements 6to Si, their potential likewise being positive with respect to thecathode 4. The magnetic field may be obtained from a suitable structurecomprising a set of four coils 2B having four equally spaced poles 2 l.A magnetic core 22, for example of iron, surrounds the tube l andpreferably has a depth substantially equal to the electrode assembly 2.Diametrically opposite coils 2e are connected, the arrangement beingthat opposite poles 2i are opposite in polarity.

The coils 2u may be connected to be excited by two-phase alternatingcurrent source, such an alternator, which effects the rotations of themagnetic field and the consequent shifting of the electron beams Iaround the periphery. If the neld is rotated continuously, the beamswill be rotated continuously and will move around the anodes producingcurrents of sine-wave form in the circuits connected to the anodes. Thisarrangement of magnetic eld serves both to focus the beams and to directthem to successive or various points on the anode periphery.

The geometry of my radial beam tube disclosed herein is not verycritical, and one may get suilicient data for designing the tube fromthe references mentioned above. The devices included as part of the tubecircuit organization may be of conventional design, since the inventionrelates primarily to the generation of tones for an electronic organ bythe application of a radial beam vacuum tube as the tone generator.

In my tone generator system, which is especially applicable to anelectronic organ such as disclosed in the aforesaid Hammond Patent No.1,956,356, I propose to use twelve master oscillators 25, which may beof the resistance-capactance type or inductance-capacitance type. Thefunction of the oscillators 25 is to generate the `first submultiples ofthe twelve fundamentals of the musical scale. Figs. 28 and 28a of theHammond Patent No. 1,956,350 constitute a chart usable in conjunctionwith his wiring diagram to indicate the connections not shown in saiddiagram and includes data utilized to drive the tone generators of hissystem, an explanation of this chart being given in lines 118 to 156,page 3, and lines 1 to 15, page 9 of the patent. A feature of the chartis the comparison of the frequency of the current generated (column 8)for a given key with the theoretical frequency of note or key in anequally tempered musical scale (column 9). It will be noted that thereis close fidelity of these two frequencies for the same note, and thatfor the lower notes C, Ct', D, Dali, E, F, Ft, G, Gi?, A, A# and B, thetheoretical frequencies are 32.7, 34.6, 36.7, 38.9, 41.2, 43.6, 46.2,48.9, 51.9, 55.0, 58.3, 61.7 cycles.

In each of the master oscillators 25 the phase is split so that twophase currents of the proposed submultiple frequency are available foreach of two stators to be used in conjunction with two radial beam tubesto generate the fundamental and the 2nd, 4th, 8th, 16th, 32nd, 64th and128th harmonic tones of the fundamental. See Fig. 5.

The construction of the two radial beam tubes to be used with the twostators has been clescribed above. The rotating magnetic field reivolvesat a cyclic frequency of only one-half the fundamental, i. e., the rstsubmultiple. For ex" ample, the frequency of the first master oscillator25 will be 16.35 cycles per second.

For the higher harmonics it may be inconvenient to accommodate so manypeaks in the apertures in the screens and it may be more practical totake the 8th harmonic 'from the first tube of each set and to split itsphase and feed this frequency to the stator ofthe second tube. By thesemeans all of the radial |beam tubes would be identical in design andconstruction. The magnetic field in the stator for the second tube wouldrevolve sixteen times as fast vas that in the first stator.

The stators used with the radial beam tubes mayV be 4of conventionaldesign such as those mentioned in my prior Patents Nos.. 2,217,774 and2,320,756 referred to above. From the foregoing it will be understoodthat there will be twelve master oscillators, each connected up as shownin Fig. 5. This will require a total of twentyfour stators andtwenty-four radial beam vacuum tubes for the tone generating systemcontemplated herein.

The following brief explanation of the general operation of my tonesystem contemplated herein will probably be helpful to a fullunderstanding of the invention. The complete system consisting of thetwenty-four radial beam tubes may be connected to the keys and stops ofthe organ in a similar fashion to the connections of theelectromechanical generators of the Hammond organ. All twenty-four tubeswill be in continuous operation generating the ninety-six separate tones(of the sine-wave form) These ninety-six tones consist of the twelvelowest notes on the organ, plus the first seven harmonics of each. Thesetones are approximately equal to the eighty-nine frequencies listed incolumn 9 of Figs. 28 and 28a of the Hammond patent above referred to,plus seven additional higher harmonics. The function of the stops of theorgan is to add higher harmonics to the note that is sounded when a keyis struck. By varying the selection of the harmonics added, the timbreor quality of the tone is varied, this selection being accomplished bypulling out the different stops. As is well known in the art, any organtone may be synthesized by adding harmonics of the fundamental tone invarying proportions.

When a key is depressed, the stops having been previously set, thefundamental frequency corresponding to that note is taken from a radialbeam tube by the contact under the key and passed on to the amplifiersand finally to the loud-speaker, and, at the same time, other contacts(energized by the stop) under the key add in the preselected group ofharmonics so that the note that issues from the loud-speaker` consistsof the fundamental frequency plus its selected harmonics.

Also in continuous :operation are the twelve master subharmonicgenerators furnishing the rotating magnetic fields for the twenty-fourradial beam tubes. 'Ihe first submultiple (i. e., onehalf thefundamental frequency) is chosen for the master oscillators since thereare two beams in each radial beam tube giving the effect of one beamrotating at twice the frequency.

From the foregoing description of the embodiment of the invention shownin the drawings, it will be seen there is provided a tone generatorsystem utilizing a plurality of radial beam vacuum tubes as the tonevsource. It will be obvious that various changes may be made by thoseskilled in the art in the design of the tube and the circuitorganization in which it is incorporated, but it is desired to cover allsuch changes as come Within the scope of the appended claims.

. I c'laimz' 1. In an electronic circuit organizatiom in combination, aplurality of radial beam vacuum tubes each comprising a cathode and apluralityof anodes mounted in the cylindrical boundaryiencompassing saidcathode and coaxial therewith, means for concentrating electronsemanating from said cathode into a rotating Abeam including coils inquadrature for producing a rotating magnetic field, said field havingits lines of force normal to the longitudinal axis of said cathode, asystem of master oscillators designed to generate the submultiples ofthe fundamentals of a musical scale, the circuit arrangement/of eachmaster oscillator being split to produce -two phase currents of thesubmultiple frequency available for each of the two stators of theseveral oscillators, two of said radial beam vacuum tubes being includedin the two phase circuits of the oscillators, the several anodes beingdesigned to give respective fundamentals and produce harmonics inconjunction with the associated pair of radial beam tubes, the unrolledscreen elements of the several radial beam tubes being similar in designbut adapted to produce the various frequencies and their harmonics ofthe musical scale.

2. In an electronic circuit organization, in combination, a pair ofradial beam vacuum tubes each comprising a cylindrical indirectly heatedcathode surrounded by a coaxial cylindrical screen element, a pluralityof spaced ring-shaped anodes encompassing the screen, the screen elementhaving a series of apertures forming bands coaxially arranged withrespect to the cathode and oppositely disposed with respect to theseveral anodes, means for concentrating electrons emanating from saidcathode into a rotating beam including coils in quadrature for producinga magnetic field, said magnetic field having its lines of force normalto the longitudinal axis of said cathode, a system of master oscillatorsdesigned to generate the submultiples of the fundamentals o-f a musicalscale, the circuit arrangement of each master oscillator being split toproduce two phase currents lof submultiple frequencies available forea-ch of the two stators of the several oscillators, the pair of saidradial beam vacuum tubes being included in the phase lcircuits of theoscillators, the rotation of the magnetic field of each radial beam tubebeing continuous, whereby the circuits connected between each anode andthe cathode may be closed and opened in sequence, the magnetic fieldserving both to focus the bea-ms and to direct them to successive orvarious points on the periphery of the several anodes of each tube, thedesign of the screen element of each tube being adapted to producesine-wave currents of the various frequencies of a musical scale by therotation of the electron beams.

3. An electron discharge device having an evacuated enclosing envelopecontaining an electrode assembly, said assembly comprising a centralelongated electron-emitting cathode, a plurality of individual anodesconcentric with relation to the cathode and arranged in spaced tiersextending along the length of the cathode, an electron baille electrodeconcentric with respect to the cathode and located between the cathodeand said anode, said baille having a series of windows arranged in tierswith each tier in radial alignment with one of said anodes, individuallead-ins for said anodes, and a common rotating field producing meansfor all said anodes for forming the electron from the cathode into arotating REFERENCES CITED The following references are of record in thele of this patent:

Number UNITED STATES PATENTS Name Date Thompson Mar. 29, 1932 HammondApr. 24, 1934 Karolus June 12, 1934 Davis Sept. 8, 1936 Skellett Oct.15, 1940 Gray Oct. 7, 1941 Stuart, Jr. Aug. 18, 1942 Skellett June 1,1943 Hecht et al J-an. 1, 1946

